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ELM329P 参数 Datasheet PDF下载

ELM329P图片预览
型号: ELM329P
PDF下载: 下载PDF文件 查看货源
内容描述: CAN解释 [CAN Interpreter]
分类和应用:
文件页数/大小: 76 页 / 353 K
品牌: ELM [ ELM ELECTRONICS ]
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ELM329  
Selecting Protocols  
The ELM329 supports several different OBD  
Protocol  
Description  
Automatic  
protocols (see Figure 2, at right). This is a little  
misleading however, as the ELM329 only provides  
very minimal support for protocols 1 to 5 - they are  
only included so that most ELM327 software will still  
work with the ELM329.  
The ELM329 really only provides extensive  
support for CAN protocols 6 to F. You may never need  
to actually select one of these, since the factory  
settings cause an automatic search to be performed  
for you, and the protocol is activated if it seems  
appropriate. If experimenting, you will wish to be able  
to select a protocol, however.  
For example, if you know that your vehicle uses  
the ISO 15765-4, with an 11 bit ID and a rate of  
500kbps (protocol #6), then you may want the ELM329  
to use only that protocol, and no others. If that is what  
you want, simply use the ‘Set Protocol’ AT Command  
as follows:  
0
1
2
3
4
5
6
7
8
9
A
B
C
D
E
F
SAE J1850 PWM (41.6 kbaud)  
SAE J1850 VPW (10.4 kbaud)  
ISO 9141-2 (5 baud init)  
ISO 14230-4 KWP (5 baud init)  
ISO 14230-4 KWP (fast init)  
ISO 15765-4 CAN (11 bit ID, 500 kbaud)  
ISO 15765-4 CAN (29 bit ID, 500 kbaud)  
ISO 15765-4 CAN (11 bit ID, 250 kbaud)  
ISO 15765-4 CAN (29 bit ID, 250 kbaud)  
SAE J1939 CAN (29 bit ID, 250* kbaud)  
User1 CAN (11* bit ID, 125* kbaud)  
User2 CAN (11* bit ID, 50* kbaud)  
SAE J1939* CAN (29* bit ID, 500* kbaud)  
User4 CAN (11* bit ID, 95.2* kbaud)  
>AT SP 6  
OK  
From this point on, the default protocol (used after  
every power-up or AT D command) will be protocol 6  
(or whichever one that you have chosen). Verify this  
by asking the ELM329 to describe the protocol:  
User5 CAN (11* bit ID, 33.3* kbaud)  
*user adjustable  
>AT DP  
ISO 15765-4 (CAN 11/500)  
Figure 2. ELM329 Protocol Numbers  
Now what happens if your friend has a vehicle that  
uses a different baud rate? How do you now use the  
ELM329 interface for that vehicle, if it is set for your  
car?  
One possibility is to change your protocol selection  
to allow for the automatic searching for another  
protocol, on failure of the current one. This is done by  
putting an ‘A’ before the protocol number, as follows:  
affects the setting for the next powerup, and may not  
actually be appropriate, if the protocol selected is not  
correct for the vehicle. To allow a test before a write  
occurs, the ELM329 offers one other command - the  
Try Protocol (TP) command.  
Try Protocol is very similar to Set Protocol. It is  
used in exactly the same way as the AT SP command,  
the only difference being that a write to internal  
memory will only occur after a valid protocol is found,  
and only if the memory function is enabled (M0/M1).  
For the previous example, all that needs to be sent is:  
>AT SP A6  
OK  
>AT DP  
>AT TP A6  
OK  
AUTO, ISO 15765-4 (CAN 11/500)  
Now, the ELM329 will try protocol 6, but will then  
automatically begin searching for another protocol  
should the attempt to connect with protocol 6 fail (as  
would happen when you try to connect to your friend’s  
vehicle).  
The Set Protocol commands cause an immediate  
write to the internal EEPROM, before even attempting  
to connect to the vehicle. This write is time-consuming,  
Many times, it is very difficult to even guess at a  
protocol to try first. In these cases, it is best to simply  
let the ELM329 decide what to use. This is done by  
telling it to use protocol 0 (with either the SP or the TP  
commands).  
To have the ELM329 automatically search for a  
protocol to use, simply send:  
ELM329DSB  
Elm Electronics – Circuits for the Hobbyist  
www.elmelectronics.com  
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